FIELD OF THE INVENTION
The present invention is related to a binocular having parallel telescopic optical systems with focusing and power-varying mechanisms and mechanisms for interpupillary adjustment, diopter difference adjustment, and independent magnification adjustment.
Binoculars have parallel telescopic optical systems that are usually angularly movable to vary the distance between the eyepieces for interpupillary adjustment.
Generally, two telescopic optical systems are hinged to each other by a shaft for angular movement about respective optical axes that extend parallel to the shaft. When the telescopic optical systems are turned about the optical axes, they are moved toward or away from each other to bring the eyepieces to a suitable interpupillary distance for the user of the binocular.
According to a modern binocular design, the telescopic optical systems have respective Porro prisms as erector prismatic systems, respective objectives, and respective eyepieces whose optical axes are displaced out of alignment with those of the objectives. The telescopic optical systems are angularly movable about the optical axes of the objectives for interpupillary adjustment.
Binoculars are required to have some synchronizing mechanism for focusing the telescopic optical systems in ganged relationship to each other. Power-variable binoculars, or zoom-type binoculars, are also required to be equipped with a synchronizing mechanism for synchronously varying the magnifications of the telescopic optical systems. To vary the magnifications of the telescopic optical systems in synchronism with each other, the synchronizing mechanism moves power-varying lenses associated with eyepiece assemblies along respective optical axes to continuously vary the focal length of lenses ranging from objectives to eyepieces.
Since the telescopic optical systems are angularly movable for interpupillary adjustment, as described above, the synchronizing mechanisms for adjusting the focus and varying the magnification should operate to synchronize the telescopic optical systems without inhibiting the angular movement of the telescopic optical systems for interpupillary adjustment. To meet such a requirement, it has been customary for the synchronizing mechanisms to have a rather complex structure especially for use in binoculars whose telescopic optical systems have respective eyepieces whose optical axes are displaced out of alignment with those of the objectives because the eyepieces are turned about the optical axes of the objectives.
As a consequence, the synchronizing mechanisms are relatively large in size, resulting in a large binocular size. The user of the binocular is required to exert large manual forces to actuate the synchronizing mechanisms.
Motor-driven binoculars which electrically actuate the synchronizing mechanisms are also large in size since they require motors and batteries.
Binoculars with parallel telescopic optical systems generally have a focusing mechanism for moving both eyepieces simultaneously along their optical axes, and a diopter difference adjusting mechanism for moving one of the eyepieces independently of the other eyepiece. The diopter difference adjusting mechanism is used to compensate for vision errors of the user. After the diopter difference is eliminated using the diopter difference adjusting mechanism, the telescopic optical systems are brought into an in-focus condition by the focusing mechanism.
According to the modern binocular configuration with the telescopic optical systems being angularly movable about the optical axes of the objectives for interpupillary adjustment, a focusing mechanism is associated with the objectives for the reason that the interaxial distance between the objectives remains unchanged regardless of the interpupillary adjustment. However, since a diopter difference adjusting mechanism is still coupled to one of the eyepieces, that eyepiece must be movable only for the purpose of diopter difference adjustment. The binocular structure is relatively complex and costly because of the diopter difference adjusting mechanism.
The magnifications, or powers, of the telescopic optical systems of power-variable binoculars must be equalized to each other at all times. For equalizing the magnifications of the telescopic optical systems, it is necessary to adjust them with respect to each other. Inasmuch as the power-variable binoculars have a synchronizing mechanism for synchronously varying the magnifications of the telescopic optical systems, however, it is impossible to adjust the magnifications independently of each other. Heretofore, the magnifications of the respective telescopic optical systems must be adjusted independently before the synchronizing mechanism is assembled or after the assembled synchronizing mechanism is disassembled. Accordingly, the conventional independent magnification adjustment process has been tedious and time-consuming.